A conventional, roughly circular cylindrical magnetic resonance tomograph (MRT) includes, from a radially outer side to a radially inner side, a basic magnetic field coil for creating a constant permanent-magnetic or electromagnetic basic field (B0), three gradient coils for creating linearly increasing or decreasing electromagnetic gradient fields (Bx, By, Bz) in the three spatial directions x, y, z, and a substantially cylindrical body coil (BC) for creating an electromagnetic RF alternating field (B1) via at least one RF feed line. The body coil (BC) may be operated as a transmit and/or receive antenna (e.g., a transmit antenna). In the inner chamber of the magnetic resonance tomograph surrounded by the coils (a.k.a. the patient tunnel), a patient table may be moved into the tunnel from the patient side and moved out of the tunnel again. The MRT scan is performed while the patient table is moving or at a standstill. Smaller local coils (LC) that may be operated as transmit and/or receive antennae (e.g., receive antennae) may be disposed on the patient table or on the patient.
The body coil (BC) is formed from copper or a similar material and may be configured as a birdcage antenna. The BC may have two end rings with a plurality (e.g., 4, 8, 16 or 32) of rungs lying between the two end rings. This structure may be applied as copper wires to a cylindrical tube as a type of circuit board. Both the end rings and the rungs have various electrical components (including capacitors) that have the effect of electrically separating the part sections of the end rings or rungs. A few of the capacitors are configured as trimmer capacitors. The trimmer capacitors have capacitor plates that may be rotated in relation to one another. The capacitance C of the trimmer capacitors may be varied through the capacitor plates. As a result, the electrical resonant circuit (e.g., the body coil BC, electrical components and RF feed lines of the BC, and one of the two or more RF voltage sources) may be changed and brought into resonance as a function of the radio frequency voltage applied in a process referred to below as the “tuning process” or “tuning.” Only physical variables of the electrical components of the electrical resonant circuit are changed (e.g., the capacitances of the trimmer capacitors).
A tuning process of a type described above is performed after manufacture and during commissioning of the MRT, and also at regular intervals during operation (e.g., about every 6 months) by a service person.
The tuning of the BC is a tedious, multidimensional process that is performed by a service engineer under great stress and time pressure. The main work sequence involves turning the variable capacitors or capacitances (e.g., trimmer capacitors) of the BC to maintain the resonant frequencies and the decoupling factor of the manufacturer's specification/requirements. At present, a BC has two feed channels that are largely tuned individually. As a result, a mutual coupling (also called “decoupling”) of the RF feed channels is adjusted.
On the service side opposite the patient side, a service person turns the trimmer capacitors between the gradient coil system and the BC with a very long screwdriver of about 50 cm, and reads off the new values from a display of the console on the patient side. This process may be repeated 3 to 7 times for each radio frequency to be tuned. The same process may also be performed for the decoupling of the RF feed channels. Sometimes, after a good decoupling has been achieved, the frequencies are tuned again even more finely since one tuning affects the other tuning.
In most current devices, the number of RF feed channels to be tuned is only two. However, multi-channel systems (e.g., eight channels or more) exist. The tuning of such multi-channel systems is difficult since all RF feed channels are tuned individually and, in each case, decoupled in relation to one another.
A problem in the conventional tuning method (e.g., sitting down, turning the capacitors, standing up, pressing the button and waiting for results) is that real-time information is not fed back to the service person. In addition to the large amount of time expended, the method does not deliver any immediate feedback about the result of the tuning to the service person. Since the service person receives the result only after a delay (e.g., going to the front side of the magnets, pressing the button, and waiting), the results of the service person's tuning efforts cannot form a feedback loop (e.g., with the service person located in the middle).
Another problem is that the service person is forced to remember the old numbers of a previous tuning process and to perform mental calculations to decide whether a tuning being performed is in the right direction for improvements or is moving away from the specification/requirement.
A further problem is that the service person is working with a screwdriver close to parts (e.g., electrical lines of the gradient coils) that carry high voltages when the magnetic resonance tomograph is operating. Although these areas are grounded during the tuning, a high level of concentration is called for by the service person that is visually focused on the area wherein the screwdriver is being used.